Various striping or marking compositions have been used on roads and highways for many years. The first class of striping compositions used on roads and highways with some success were alkyd-based paint compositions such as those disclosed in U.S. Pat. Nos. 2,897,732; 2,897,733; and 3,326,098. Alkyd-based paint compositions are generally slow to dry and contain ester linkages which are susceptible to hydrolysis from the alkaline condition of roads. This hydrolysis, in part, causes the applied paint to have poor wear resistance. Accordingly, it is desireable to provide a striping composition having a much faster cure time and improved wear resistance.
Most alkyd-based paint compositions require the addition of a solvent or drying oil to decrease the viscosity so that the paint composition can be sprayed onto road surfaces. For example, see U.S. Pat. No. 3,326,098. The presence of a solvent during highway marking creates a pollution problem since the solvent evaporates into the atmosphere. Accordingly, it is desireable to provide a striping composition which is 100% solids, and does not contain solvents or drying oils.
As an alternative to alkyd-based paint compositions, solvent free epoxy-based striping compositions were developed. Epoxy-based striping compositions are described in detail in U.S. Pat. Nos. 4,088,633; 4,185,132; and 4,255,468. These striping compositions are a significant improvement over prior alkyd-based paints in terms of alkaline and wear resistance, and in reducing the need for solvents during application. In particular, the epoxy-based striping compositions are better at withstanding water immersion compared with the alkyds. In addition, they provide a better bond to glass beads dropped thereon which is important for providing retroreflectivity at night. Increased adhesion to glass beads provides better retention of the glass beads to the road surface for a longer period of time. Epoxy-based striping compositions, however, are still generally too slow in curing, particularly on a cold road surface. In addition, they age harden and become brittle, and have a tendency to amber. As a result of the slow curing rate for such epoxy-based striping compositions, it is necessary to put cones along the striping composition applied to a road surface to prevent cars traveling along the road from tracking the uncured composition. The necessity for coning while the epoxy-based striping composition cures increases the cost of striping a road by requiring a number of cones sufficient to prevent cars and trucks from tracking the striping composition before it cures, and by providing the necessity for employing crews to put the cones down once the striping composition is applied and to pick the cones up once it cures. Accordingly, it would be desirable to stripe a road with a composition that is fast cure, even on cold road surfaces, in order to eliminate the need for coning and thereby enhance striping efficiency.
Furthermore, it would be desireable to provide a fast cure striping composition having good adhesion characteristics to road or highway surfaces and which can withstand weathering and which will not significantly amber over time.